External coil assembly for a transcutaneous system

ABSTRACT

An external coil assembly for a transcutaneous system is disclosed. The assembly comprises: a housing having a skin-adjacent surface, an opposing exposed surface and a threaded shaft open to the exposed surface and extending toward the skin-adjacent surface; an external coil secured within the housing; and a magnet with a threaded exterior surface to threadingly engage the threaded shaft, wherein at least one of either the shaft thread or the magnet thread has at least one transverse channel forming discontinuities in the thread.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/214,908 filed Aug. 31, 2005, which is now U.S. Pat. No.8,428,723, which is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 29/206,716, entitled “Magnet Housing for Coil,”filed Jun. 3, 2004, which is now U.S. Pat. No. D512,406, which is herebyincorporated by reference herein in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates generally to transcutaneous systems, andmore particularly, to an external coil assembly of an transcutaneoussystem.

2. Related Art

The use of implantable medical devices to provide therapy to individualsfor various medical conditions has become more widespread as theadvantages and benefits such devices provide become more widelyappreciated and accepted.

Medical devices designed for temporary or permanent implantationinclude, for example, cardiac assist or replacement devices such aspacemakers, defibrillators, circulatory assist devices and artificialhearts; stimulating devices such as cochlear™ implants, neuromuscularsimulators, bone growth stimulators. etc; biosensors, and others. Mostimplantable medical devices that perform work (active devices) and manyof those that do not (passive devices) require power.

For those that require more power than can reasonably be provided by animplantable energy storage device, power must be transferred to theimplanted device during its operational life. Traditionally, apercutaneous lead has been used to effect such power transfer. However,due to the high incidence of infection and other drawbacks,inductively-coupled transcutaneous energy transfer (TET) systems aremore commonly utilized to provide the requisite power to an implanteddevice. Transcutaneous systems have also been utilized to transfer dataadditionally or alternatively to power.

A variety of arrangements have been developed or proposed fortranscutaneous transmission of data or power. For example, in additionto providing power, transcutaneous energy and information transmission(TEIT) systems are used to transfer data utilizing theinductively-coupled coils or a separate, integrated device such as aninfra-red (IR) communication device. For example, in some cochlear™implants a radio frequency link is established between the coils of atranscutaneous system to transmit encoded stimulus information to aninternal receiver that delivers the stimuli to electrodes implanted inthe cochlear. These and other systems which include the use ofinductively-coupled coils are generally and collectively referred toherein as transcutaneous systems.

Generally, the subcutaneous coil is implanted just beneath the surfaceof the skin, while the external coil is located on the skin surface inalignment with the implanted coil. Because efficient energy transferrequires the coils to be aligned, various approaches have been developedto maintain such alignment between the external and implanted coils.Such previous approaches include ear hooks, headgear, pegs, VELCRO™,clips, skin pouches, and other mechanical alignment systems. Theseapproaches suffered from poor alignment and increased possibility ofinfection. More recently, these approaches have been surpassed with theuse of attractive magnets fixed relative to the internal and externalcoils. For example, in cochlear™ implants, an internal coil and magnetare surgically secured to the cranium while the external coil is held onthe scalp in alignment with the implanted coil by a magnet.

SUMMARY

In accordance with one aspect of the present invention, an external coilassembly for a transcutaneous system is disclosed. The assemblycomprises: a housing having a skin-adjacent surface, an opposing exposedsurface and a threaded shaft open to the exposed surface and extendingtoward the skin-adjacent surface; an external coil secured within thehousing; and a magnet with a threaded exterior surface to threadinglyengage the threaded shaft, wherein at least one of either the shaftthread or the magnet thread has at least one transverse channel formingdiscontinuities in the thread.

In accordance with another aspect of the present invention, a magnet isdisclosed. The magnet comprises: an exterior surface having a threadconfigured to engage a threaded shaft in an external coil assembly of atranscutaneous system, wherein the magnet thread has at least onetransverse channel forming discontinuities in the thread.

In accordance with a further aspect of the present invention, anexternal coil assembly for a transcutaneous system is disclosed. Thesystem comprises: housing means for housing an external coil of atranscutaneous system, the housing means having a skin-adjacent surface,an opposing exposed surface and a threaded shaft open to the exposedsurface and extending toward the skin-adjacent surface; and magnet meanshaving a threaded exterior surface for threadingly engaging the threadedshaft, wherein at least one of either the shaft thread or the magnetthread has at least one transverse channel forming discontinuities inthe thread.

In accordance with a still further aspect of the present invention, amethod for facilitating removal of debris accumulating between a magnetand a housing of an external coil assembly of a transcutaneous system isdisclosed. The method comprises: providing at least one transversechannel in the housing; and collecting debris which accumulates betweenthe housing and the magnet in one or more of the at least one transversechannel.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a perspective view of an exemplary prosthetic hearing implantsystem in which embodiments of the present invention may beadvantageously implemented;

FIG. 2A is a perspective view of a proximal side of an externaltransmitter unit in accordance with an embodiment of the presentinvention;

FIG. 2B is a perspective view of one embodiment of a distal side of theexternal transmitter unit shown in FIG. 2A;

FIG. 2C is a bottom view of one embodiment of the proximal side of theexternal transmitter unit shown in FIG. 2A;

FIG. 2D is a cross-sectional view of one embodiment of the external coilhousing shown in FIG. 2C;

FIG. 3A is a perspective view of one embodiment of an exposed side of anexternal coil housing with an embodiment of a magnet configured to beinserted into the housing in accordance with an embodiment of thepresent invention;

FIG. 3B is a perspective view of one embodiment of the external coilhousing with the magnet threadingly engage in the threaded shaft ofhousing as shown in FIG. 3A;

FIG. 3C is a cross-sectional view of one embodiment of the external coilhousing shown in FIG. 3B;

FIG. 4A is a cross-sectional view of a transverse channel in accordancewith one embodiment of the present invention;

FIG. 4B is a cross-sectional view of a transverse channel in accordancewith an alternative embodiment of the present invention; and

FIG. 5 is a perspective view of a magnet having an exterior thread withtransverse channels therein in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

The present invention is generally directed to a housing for an externalcoil of a transcutaneous system. The housing has a skin-adjacentsurface, an opposing exposed surface and a threaded shaft open to theexposed surface and extending toward the skin-adjacent surface. Anexternal coil is secured within the housing. A magnet having a threadedexterior surface to threadingly engage the threaded shaft is alsoprovided. In accordance with the teachings of the present invention,either or both the shaft thread or the magnet thread has/have at leastone transverse channel forming discontinuities in the thread.

Advantageously, the transverse channel(s) accumulate/s and collect/sdebris that may become lodged between neighboring portions of the shaftor magnet threads. This provides for easier adjustment of the magnet inthe housing, as well as removal and replacement of the magnet. Also, thechannel(s) is/are accessible to the recipient, facilitating removal ofthe debris by the recipient using, for example, a finger, pen, needle,knife, scissors, or other suitable item. It is noted that the above andadditional or alternative embodiments are provided by embodiments of thepresent invention without compromising the mechanical integrity of theexternal coil assembly.

There are several types of medical devices that include temporarily- orpermanently-implanted components that, when implanted, exchange data orpower with external components using a transcutaneous system. Suchmedical devices include but are not limited to cardiac assist orreplacement devices, stimulating devices, biosensors, and the like.

The present invention will be described in conjunction with one suchmedical device, a prosthetic hearing implant, such as a Freedom™,Nucleus™ or Cochlear™ implants sold by Cochlear Limited. Such devicesare described in U.S. Pat. Nos. 4,532,930, 6,537,200, 6,565,503,6,575,894, and 6,697,674, the entire contents and disclosures of whichare hereby incorporated by reference. It should be understood to thoseskilled in the art that the present invention may be used intranscutaneous systems implemented in any of the above or otherimplantable medical devices.

FIG. 1 is a schematic diagram of an exemplary prosthetic hearing implantsystem 100 in which embodiments of the present invention may beimplemented. Implant system 100 comprises external components 102 whichare directly or indirectly attached or secured to the recipient, andinternal components 104 which are implanted adjacent to and in the ear106 of the recipient. For simplicity, ear 106 is shown to comprise acochlea 110 and an acoustic nerve 112.

External components 102 comprise a microphone 120 for detecting sounds,a speech processor 122 that converts the detected sounds into a codedsignal, a power source (not shown), and an external transmitter unit124. External transmitter unit 124 comprises an external coil 126 and amagnet 128 secured to external coil 108 in housing 130. Speech processor122 processes the output of microphone 122. Speech processor 122generates a coded signal which is provided to external transmitter unit124 via cable 132.

Internal components 104 comprise an internal receiver unit 140, astimulator unit 142, and an electrode assembly 144 having an electrodearray 146. Electrode assembly 144 extends into cochlea 110 and providesthe coded signal to the nerve fibers (not shown) through electrode array146. This stimulates hearing for a recipient with damage to cochlea 110,or surrounding tissue and/or nerves. Internal receiver unit 140comprises an internal coil 148 and a magnet 150 fixed relative tointernal coil 148. Internal coil 148 receives power and data,represented by arrow 160, from external coil 124 through the skin 170 ofthe recipient.

The efficiency of the transcutaneous link 160 is determined by a numberof factors one of which is the extent to which external and internalcoils 126, 148 are aligned. That is, as the relative lateral offsetbetween external and internal coils 126, 148 increases, the efficiencyof the magnetic coupling of the coils decreases.

In the exemplary embodiments described herein, internal coil 148 isaligned with external coil 124 using magnets 128 and 150. Since theattractive magnetic force between magnet 128 and magnet 150 is notpermanent, external transmitter unit 124 may be removed and adjusted.Although magnets 128, 150 provide sufficient coupling strength to holdexternal coil 126 in alignment with internal coil 148, it is oftentimesdesirable to adjust the attractive forces between the internal andexternal magnets 128, 150 so that the alignment is maintained despitedifferent environmental conditions and recipient activity.

Embodiments of the present invention described below utilize a threadedshaft in the external coil housing and a magnet having reciprocalthreads to provide the recipient with the capability of adjusting theattractive force between the magnets as needed or desired. As shown byFIG. 1, external transmitter unit 124, including external coil 126,housing 130 and magnet 128, rests against skin 170 of the recipient andmay be in contact with dirt, oil, particles and other debris. Further,the surface of external transmitter unit 124 not resting against skin170 may be exposed to hair, headwear, etc. (not shown) which coversexternal transmitter unit 124 and may also contain dirt, oil, particlesand other debris. The environment, such as wind, rain, etc., also may bein contact with the exposed surface of external transmitter unit 124.Thus, housing 130 and its magnet 128 are exposed to debris originatingfrom opposing sides of housing 130.

Over repeated and continuous use, the recipient may accumulate debrisbetween housing 130 and magnet 128 which may lead to a decreasedperformance and comfort of external transmitter unit 124. In addition,such debris may decrease the sanitary environment for implant system100, especially after surgery in the same location. In particular, theaccumulate debris in the space separating housing 130 from magnet 128may lodge magnet 128, making it difficult to adjust or remove magnet 128without applying an excessive force. Without the ability to easilyadjust or remove magnet 128, the recipient may accidentally crack orbreak housing 130, external coil 124, or other components of externalunit 102 when trying to adjust or remove magnet 128. Replacing orrepairing such components is usually more expensive than replacing orfixing magnet 128.

Exemplary embodiments of the present invention will be described indetail below with reference to FIGS. 2A-2D. FIG. 2A is a perspectiveview of a skin-adjacent side of an external coil assembly housing inaccordance with one embodiment of the present invention. FIG. 2B is aperspective view of one embodiment of an exposed side of the externalcoil assembly housing shown in FIG. 2A. FIG. 2C is a bottom view of oneembodiment of the skin-adjacent side of the external coil assemblyhousing shown in FIG. 2A. FIG. 2D is a cross-sectional view of oneembodiment of the external coil assembly housing shown in FIG. 2C.

An external coil assembly 220 comprises a housing 202 having askin-adjacent side 234 and an opposing exposed side. An external coil212 is secured or otherwise integrated in housing 202. In the exemplaryembodiment shown in FIGS. 2A-2D, external coil 212 is located along aperipheral region 210 of housing 202 to define an outer ring of externalcoil assembly 220. Along peripheral region 210 there are a series ofoptional dimples 216 adapted to rest against skin 170 of a recipient.External coil assembly 202 is connected to speech processor 122 throughcable 132 via port 218.

In a raised interior region of external coil housing 202 there is ashaft 204 having a raised helical rib, or thread 236. In the embodimentshown in FIGS. 2A-2D, threaded shaft 204 terminates at a proximal rim230 which opens to the skin-adjacent side 234 of housing 202, andterminates at a distal rim 232 which opens to the exposed side ofhousing 202. As one of ordinary skill in the art would appreciate,threaded shaft 204 may open to only one side of housing 202 to allow forremoval of the magnet (not shown), as well as to allow for the recipientto remove debris in the transverse channels 208, as described elsewhereherein.

In the embodiment shown, there are portions of housing 202 which areremoved to facilitate ventilation of external coil assembly 220 when inoperation on a recipient. This results in the formation of support arms214 connecting the interior and peripheral regions of housing 202.

At least one transverse channel 208 is formed in thread 236, causingdiscontinuities in the thread. In the embodiment illustrated in FIGS.2A-2D, there are three transverse threads 208 radially distributedaround shaft 204. As one of ordinary skill in the art would appreciatefrom the present description, however, any quantity of transversechannels 208 may be implemented depending on a variety of factors suchas the anticipated quantity of debris, the mechanical integrity that isto be maintained between the magnet (not shown) and housing 202, etc.Such transverse channels 208 may be located at any absolute or relativeposition around shaft 204. In one particular embodiment, a plurality oftransverse channels 208 are radially distributed in evenly spacedincrements around shaft thread 236, as represented by angle θ in FIG.2C.

Also, in the illustrative embodiment, transverse channels 208 extendsubstantially parallel to the axis of shaft 204 and, thereforesubstantially perpendicular to a plane parallel to the helical turns ofthread 236. As one of ordinary skill in the art would appreciate, inalternative embodiments, one or more transverse channels 208 may be atany angle relative to the axis of shaft 204 and the helical plane ofthread 236 depending on the particular application, performance,environment, and other factors.

Thread 236 defines an inner diameter measured between the apex ofopposing portions of the thread, and an outer diameter measured betweenthe base of opposing portions of the thread.

Thread 236 may be a triangle-shaped thread, a square-shaped thread or atrapezoid-shaped thread, or other shape, depending on the particularapplication and desired accuracy. In respect to thread standards,embodiments of thread 236 may be compliant with metric thread, unifiedthread and other thread standards now or later developed.

Transverse channels 208 comprise a bottom wall and opposing side wallsas shown in FIGS. 4A and 4B. Transverse channels 208 may have anycross-sectional shape. For example, in one embodiment, the side andbottom walls are planar and substantially orthogonal to each other. Inan alternative embodiment, the side and bottom walls are curved to forma U-shaped cross-section. In the embodiments shown in FIGS. 4A and 4B,the planar side walls are at an approximate 60 degree angle with thebottom wall. In addition, the cross-sectional shape of transversechannels 208 may vary or may be the same between a plurality oftransverse channels 208.

As noted, in one embodiment, transverse channels 208 create periodicbreaks or discontinuities in thread 236. In one embodiment, the sidewalls are formed by the exposed sides of portions or segments of thread236 while the bottom wall is formed by the surface of shaft 204 definingthe outer diameter of shaft thread 236. A cross-sectional view of suchan embodiment is illustrated in FIG. 4A. In an alternative embodiment,one or more of transverse channels 208 is/are recessed in the wall ofshaft 204 defining the outer diameter of shaft thread 236. Across-sectional view of such an embodiment is illustrated in FIG. 4B. Itshould be appreciated by those of ordinary skill in the art that anycombination of transverse channel depth may be implemented among theplurality of transverse channels, and that the transverse channels mayhave any depth appropriate for a particular application, environment,performance, etc. For example, the dimensions of one or more transversechannels 208 may be configured to accommodate anticipated debris havingcertain dimensions.

In a further embodiment, channels 208 may extend along a portion or theentire length of shaft 204. In the embodiment shown in FIGS. 2A-2D,channels 208 are open to the exposed and skin-adjacent sides of externalcoil housing 202. It should be appreciated, however, that transversechannels 208 may not be open to one or both surfaces, and may extendalong only a portion of shaft 204. Furthermore, not all transversechannels 208 need to be the same length or open to the same surface ofhousing 202.

In a further embodiment, transverse channels 208 may be formed by orcoated with a material that facilitates the migration of debris alongthe channels to the opening at the exposed or skin-adjacent surfaces ofexternal coil housing 202.

In FIG. 3A there is shown a perspective view of external coil housing302 having a threaded shaft 304 for mating with magnet 306 along withthree transverse channels 308 disposed within threaded shaft 304.External coil housing 302 comprises an outer ring 310, having dimples316, external coil 312 which is connected to housing 304 by support arms314, and port 318 for connecting external coil housing 302 to a speechprocessor (not shown). In this embodiment, threaded shaft 304 terminatesat a proximal rim 330 and a distal rim 332, and has a cylindrical wall334 with a thread 336. Extending substantially perpendicular to the axisof shaft 304 are transverse channels 308. A cylindrical magnet 306 hasan exterior surface 354 with a thread 356 configured to threadinglyengage threaded shaft 304. A proximal end 350 of magnet 306 is insertedinto the opening of shaft 304 and rotated to engage threads 256 and 336.

Magnet 306 may be inserted, removed, or adjusted using any suitabletechnique or tool. For example, means for rotating magnet 306 may beprovided at distal end 352, such as a textured surface to facilitategripping with a finger surface, or a slot to receive a screw driver.These and other known features may be implemented to enable magnet 306to be threadingly engaged to a desired location in shaft 304.

Although magnet 306 is shown being inserted, removed or adjusted from adistal side in FIG. 3, the magnet may also be inserted, removed oradjusted from the skin-adjacent side of coil housing 302. In suchembodiments, the same or different features may be provided tofacilitate such adjustment.

Further, the length of magnet 306 may vary depending on the application,desired attractive force, requirements of the recipient, shape of theexternal coil housing, etc. In some applications, it may be necessary touse a combination of magnets to obtain the desired coupling of theinternal and external coils.

In FIG. 3B magnet 306 is threadingly engaged in shaft 304 such thatdistal surface 350 is approximately flush with the skin-adjacent surfaceof exterior coil housing 302. In this embodiment, when magnet 306 isthreadingly engaged with shaft 304, transverse channels 308 areaccessible within housing 302, even though magnet 306 is present.Further transverse channels 308 maintain a gap between shaft 304 andmagnet 306.

An accessible transverse channel 308 provides benefits for the recipientby providing a means for cleaning the mated threads of magnet 306 andshaft 304. Further, channels 308 may allow for the collection ofaccumulated debris when magnet 306 is inserted, removed or adjusted. Thecollection of debris provides a “self-cleaning” mechanism, since therotation of magnet 306 may bias the debris out of an open end of channel308. Further, once channels 308 collect debris, the recipient may cleanthe debris by removing the debris from the channels 308.

One advantage of the embodiments of the present invention is that thechannels in the housing of the external transmitter do not require anewly designed magnet. Thus, conventional magnets may be used with theembodiments of the present invention without having to obtain speciallydesigned magnets.

FIG. 5 shows an alternative embodiment of the present invention, inwhich a magnet 502 has transverse channels 504 disposed through thread506. Thread 506 is on the exterior surface of a cylinder 510 of magnet502. Transverse channels 504 are substantially perpendicular to theplane of and between the proximal surface 512 and distal surface 514 ofmagnet 502, although they need not be so in alternative embodiments.Such an embodiment provides similar advantages as the above-describedembodiments, and allows magnet 502 to be used with conventional externalcoils assemblies having a threaded housing.

As one of ordinary skill in the art would appreciate, any and all of theabove features of the transverse channels are applicable in and desiredcombination when the transverse shaft is implemented in magnet 502. Itshould also be appreciated that in alterative embodiments, anycombination of any embodiment of transverse channels may be implementedon both the threaded shaft of the external coil housing and the exteriorsurface of the corresponding magnet.

All documents, patents, journal articles and other materials cited inthe present application are hereby incorporated by reference.

Although the present invention has been fully described in conjunctionwith several embodiments thereof with reference to the accompanyingdrawings, it is to be understood that various changes and modificationsmay be apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims, unless they departtherefrom.

What is claimed is:
 1. A method facilitating removal of debrisaccumulating between a magnet and a housing of an external coil assemblyof a transcutaneous system, comprising: providing at least onetransverse channel in the housing; and collecting debris whichaccumulates between the housing and the magnet in one or more of the atleast one transverse channel.